KR101300815B1 - Production of carbonyl fluoride - Google Patents

Abstract

Chlorodifluoromethane or trifluoromethane can be photochemically oxidized with light in the presence of chlorine, preferably with a wavelength of ≥ 280 nm to produce carbonyl fluoride which can be used as an etching gas. .

Carbonyl Fluoride, Chlorine, Photochemical Oxidation

Description

Production of Carbonyl Fluoride {PRODUCTION OF CARBONYL FLUORIDE}

The present invention relates to the preparation of carbonyl fluorides (fluorophosgene) by photochemical oxidation.

Carbonyl fluoride has been proposed as a fresh etch gas for cleaning CVD reactors. Industrial preparation is possible by heating monohalodifluoromethane; See EP-A-0 310255. Scientific literature describes photochemical oxidation of chlorodifluoromethane in the presence of chlorine; E.O. Edney and D.J. Driscoll, Int. Journal of Chemical Kinetics, vol. 24 (1992), pages 1067 to 1081. The content of HCFC-22 in the irradiation cell is in the ppm range and the pressure is 700 torr. The objective is to obtain information about the tropospheric decomposition of various halohydrocarbons.

See V.A. Kuzmenko in Zhurnal Fizicheskoi Khimi 63 (1989), pages 1911 and 1912, investigated the mixture of HCFC-22, oxygen and chlorine using an IR laser.

Journal of Geophysical Research 81 (1976), pages 5765 to 5770, R. Atkinson, GM Breuer, JN Pitts, jr. and HL Sandoval, describe the photooxidation of HCFC-22 in the behavior of these compounds in the troposphere and stratosphere. The reaction is carried out at low pressure in the presence of nitrogen dioxide and optionally N ₂ O for 20 to 80 hours.

Other authors have described the photooxidation of HCFC-22 in the presence of hydrogen peroxide.

It is an object of the present invention to specify a technically advantageously feasible process for the preparation of carbonyl fluoride, C (O) F ₂ . This object is achieved by the method of the present invention.

The method according to the invention embodies a process for producing C (O) F ₂ by photooxidizing CHClF ₂ or CHF ₃ with oxygen. The radiation source used is preferably not a laser emitter and has a spectrum that does not consist of a single wavelength but comprises at least 50 nm (ie the light fraction with the lowest wavelength and the light fraction with the highest wavelength are at least 50 nm apart). It is more preferable to use incident light having a range. At least some of the radiation is preferably in the range of 280 nm or more to the long-wave end of visible light, ie up to about 750 nm. However, this does not mean that the radiation is emitted continuously over the entire range. In this context, the term "light" is not limited to "visible light" and includes radiation outside the visible range.

Preference is given to using CHClF ₂ (HCFC-22), which is a further illustration of the present invention.

The pressure in the reactor preferably corresponds to at least ambient pressure (ie 1 bar (abs.)). It may also be higher. The pressure is preferably in the range of 1 bar (abs.) To 11 bar (abs.). The temperature is preferably in the range from 20 to 300 ° C, preferably in the range from 30 to 300 ° C, in particular in the range from 30 to 90 ° C, more particularly in the range from 50 to 90 ° C. Advantageously, the conditions associated with pressure and temperature are chosen such that the reaction mixture maintains a gaseous phase.

Very particular preference is given to operating under pressureless conditions. In the context of the present invention, the term “pressureless” means that the ambient pressure (ie about 1 bar), halohydrocarbon starting material and oxygen gas (or oxygen gas; for example air or oxygen / inert gas mixture) Which may be used) and the pressure of delivery of chlorine used and the pressure formed as a result of the hydrogen chloride gas formed in the reaction, there is no additional pressure acting on the reaction mixture. The total pressure of the reactor is then less than approximately 2 bar (absolute), depending on the delivery pressure, but less than 1.5 bar (absolute), but higher than the ambient pressure.

Unlike the prior art, HCFC-22 is present in significant amounts in the reactor, not in the ppm range. Therefore, the content of the reaction mixture is preferably at least 5 mol%, preferably at least 10 mol%.

The method can be carried out batchwise or preferably continuously. This process continuously supplies starting materials (appropriate starting compounds, oxygen-containing gases such as air or pure oxygen and pure chlorine) to the flow apparatus, and depending on the amount supplied the reaction product or reaction mixture It is removed continuously. The average residence time in the reaction conduit is advantageously from 0.01 to 30 minutes, preferably from 0.1 to 3 minutes, more preferably from 0.3 to 1.5 minutes. The optimal mean residence time dependent on factors including the type of lamp, the radiation output of the lamp and the geometrical parameters of the irradiation apparatus can be determined by simple manual experiments and analysis of the product flow, for example by gas chromatography. It may be advantageous to allow the reaction mixture to be used vigorously, for example using suitable internals in the reactor. The optimum residence time in the case of batch operation can be measured in the same way.

The process can be carried out in two preferred embodiments, specifically in the absence of chlorine, or preferably in the presence of chlorine as an initiator. In the presence of chlorine as an initiator, it is preferred not to allow a certain wavelength range, specifically less than 280 nm, to act on the reaction mixture. The above two embodiments are exemplified below.

Therefore, one embodiment relates to photooxidation in the absence of chlorine or other free radical initiators or activators. For example, irradiation takes place through quartz glass, and other components of the reactor that are not arranged between the light source and the reaction mixture are optional components, for example borosilicate glass (which filters a specific radiation fraction; see below). Can be made with Suitable emitters, for example, emit radiation in the range of from 250 to 400 nm, or up to 600 nm (the spectrum may extend beyond the upper or lower limit (eg to an area of visible light of about 750 nm)). In the absence of chlorine, it is not critical when less than 280 nm of light acts on the reaction mixture.

A further preferred embodiment relates to irradiation in the presence of elemental chlorine, wherein up to 0.5 mole of elemental chlorine per mole of CHClF ₂ is irradiated with light at a wavelength of at least 280 nm. Preference is given to using from 0.01 to 0.50 moles of chlorine, preferably from 0.03 to 0.25 moles, in particular from 0.05 to 0.20 moles of elemental chlorine per mole of CHClF ₂ .

Hydrogen peroxide, ozone or nitrogen oxides such as N ₂ O or NO ₂ are preferably not added to the reaction mixture.

The conversion, yield and selectivity are particularly high when HCFC-22 and oxygen are converted in the presence of elemental chlorine, and the activation of the irradiation is made of light having a wavelength? In this case, frequencies of less than 280 nm are essentially shielded out of the frequency spectrum. This can occur using an irradiation lamp that only emits light of wavelengths above 280 nm and / or uses means to shield frequencies below 280 nm from the emitted light. For example, it is possible to irradiate through glass which transmits only light of wavelength 280 nm or more (that is, the radiation fraction of shorter wavelength is filtered out). Suitable glass for this purpose is, for example, borosilicate glass. Suitable glasses are for example 7 to 13% B ₂ O ₃ , 70 to 80% SiO ₂ and 2 to 7% Al ₂ O ₃ and 4 to 8% Na ₂ O + K ₂ O and 0 to 5 % Alkaline earth metal oxide (in each case by weight). Known trademarks of borosilicate glass are Duran, Pyrex and Solidex.

In the irradiation, an irradiation lamp which emits only (UV) light having a wavelength of ≥ 280 nm is particularly suitable. In particular, fluorescent tubes (e.g., Philips) are very suitable. With such a lamp it is possible to carry out the irradiation through quartz glass or through the previously described glasses which filter out the radiation fraction of a relatively short wavelength. The precondition is that the lamp or tube used emits in the absorption range of the elemental chlorine. In addition to particularly suitable fluorescent tubes, it is also possible to use, for example, irradiation lamps (eg, medium-pressure or high-pressure mercury emitters), and any line in the region below 280 nm is for example light having a wavelength of at least 280 nm. Filter out by irradiation through the glass only permeable. Usable glasses have been described above. Also suitable are lamps, for example high-pressure mercury lamps, which emit predominantly within or within the preferred wavelength range of 280 nm or more, for example due to the dopant. For example, the high pressure mercury emitter has a very strong band in the region of 254 nm, which can be filtered by borosilicate glass as described above. In the case of high pressure mercury emitters doped with metal iodides, this line is very suppressed. It is surprising that when doped radiators are used, the conversion rate increases more rapidly than the direct proportion. Particularly suitable emitters are high pressure mercury emitters doped with gallium iodide, in particular thallium iodide or cadmium iodide. If such a doped radiation lamp is used, a relatively short wavelength radiation fraction with λ <280 nm is also manipulated and filtered, for example in borosilicate glass.

The molar ratio between the starting material and oxygen can vary within wide ranges, but at least 0.4 moles of oxygen per mole of starting material are suitably used. Oxygen may be used in excess. Particularly good results are achieved when the molar ratio of starting material and oxygen is in the range from 1: 0.4 to 1: 5, preferably from 1: 0.4 to 1: 1, in particular from 1: 0.4 to 1: 0.9. As mentioned, oxygen can be used in the form of air. Preference is given to using oxygen in the form of an O ₂ / inert gas mixture, in particular pure oxygen. With regard to product purity, it is preferred that a minimum amount of water is present during the reaction (eg less than 30 ppm). If desired, the reactants may remove the entrained water by known methods (eg, using molecular sieves).

An advantage of the process according to the invention is its high selectivity and yield.

The following examples illustrate the invention and are not intended to be limiting.

Example 1 Preparation of Fluorophosgene (COF ₂ ) by Photochemical Reaction

Scheme : CF ₂ HCl + ½O ₂ → COF ₂ + HCl

Batch size : see specific experiments

Experiment process and composition

The reaction chamber used is a reactor made from Duran glass with a volume of 580 ml with a cooling finger (Duran) and a lamp shaft (Quartz glass). Gas is introduced through the glass frit at the bottom of the reactor. The high pressure mercury vapor emitter was cooled with compressed air.

At the start of the experiment, the lamp was first ignited after the start of compressed air cooling. After approximately 10 minutes, the emitter reached its output (500 or 700 watts). Now the gas has been introduced. First, the introduction of HCFC-22 (R 22) was started, then chlorine was introduced, and finally oxygen was introduced, and all three reactants were introduced into the reactor.

Thereafter, all gases were simultaneously metered at a constant rate and passed through the reactor chamber (“a small amount of chlorine” means about 0.12 mol / h of chlorine per 1 mol / h of CHF ₂ Cl). Excess chlorine was removed and the resulting product gas stream was passed through a wash bottle (filled with approximately 5% H ₂ O ₂ solution) to convert it to HCl. Samples of product air stream were removed upstream of the wash bottle.

Experiment 1:

Batch: 0.5 mole R22 / h

0.5 mol of O ₂ / h

Small amount of Cl ₂

Process: 700 Watt Lamp Output

Analytical evaluation of gas samples (all assays calculated without air)

Sample:

Experiment 2:

Batch: 0.5 mole R22 / h

0.5 mol of O ₂ / h

Small amount of Cl ₂

Process: 500 Watts Lamp Output

Analytical Evaluation (all analyzes except samples at 13.30 are calculated without air)

Experiment 3:

Batch: 0.5 mole R22 / h

0.5 mol of O ₂ / h

Small amount of Cl ₂

Process: 500 Watts Lamp Output

Analytical Evaluation (all analyzes calculated without air)

Sample:

Example 2: Fluorophosgene (COF) by Photochemical Reaction ₂ Manufacturing

(With quartz glass cooling fingers, without Cl ₂ )

Experiment process and composition

The reaction chamber used was a reactor made from Duran glass with a volume of 580 ml with a cooling finger made of quartz and a lamp shaft (quartz glass). Gas was introduced through the glass frit at the bottom of the reactor. The high pressure mercury vapor emitter was cooled with compressed air. At the start of the experiment, the lamp was first ignited after the start of compressed air cooling. After approximately 10 minutes, the emitter reached its output. HCFC-22 was first introduced into the reactor followed by oxygen.

Thereafter, the two gases were simultaneously metered at a constant rate and passed through the reaction chamber. The obtained product air stream was analyzed.

Experiment 2.1:

Batch: 0.5 mole R22 / h

0.4 mol of O ₂ / h

Process: 500 Watts Lamp Output

Analytical Evaluation

Sample:

These examples show that particularly good yields and conversions are obtained when a relatively short wavelength fraction (λ <280 nm) is carried out in the presence of chlorine with filtered light.

Example 3 : Preparation of C (O) F _{2 with} a molar ratio of HCFC-22 to O ₂ of 1: 0.8

In the reactor of about 580 ml volume, HCFC-22, O ₂ and Cl ₂ were fed at a throughput of 1.0 mol / h of HCFC-22, 0.8 mol / h of O ₂ and 0.06 mol / h of Cl ₂ , A residence time of 1 minute was generated and reacted with each other at 50 ° C.

The experiment was repeated with a throughput of 0.8 mol / h HCFC-22, 0.64 mol / h 0 ₂ and 0.05 mol / h Cl ₂ .

Excellent selectivity of C (O) F ₂ of approximately 99.0 to 99.3% was obtained.

Carbonyl fluoride can be isolated by conventional methods such as low temperature distillation or pressure distillation.

Claims (9)

C (O) F ₂ is prepared by photooxidizing CHClF ₂ or CHF ₃ as oxygen as a starting compound, The molar ratio of the starting compound and oxygen is at least 1: 0.4, and light having a spectral range of at least 50 nm is irradiated, Irradiation is carried out without chlorine with incident light which may have a wavelength of less than 280 nm, or irradiation in the presence of elemental chlorine with light of a wavelength of at least 280 nm, in which case 1 mole of CHClF ₂ or CHF _{3 in the} reaction mixture Less than 0.50 mole of chlorine element per sugar. The process of claim 1, wherein 0.05 to 0.20 moles of chlorine element are present per mole of CHClF ₂ or CHF ₃ . The method of claim 1, wherein the molar ratio of the starting compound and oxygen is 1: 0.4 to 1: 5. The method of claim 1, wherein the irradiation is carried out at a temperature of 20 to 300 ° C. The method of claim 1, wherein the irradiation is carried out at a pressure of 1 to 11 bar (abs.). The method of claim 1 wherein the reactant is in the gas phase. The method of claim 1 wherein the reaction is carried out continuously. 8. The process of claim 7, wherein the average residence time in the reactor is from 0.1 to 3 minutes. The method of claim 1 wherein CHClF ₂ is used as starting material.